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BRUCE ROSEMAN, M.D.
NICOLE LIVESCU, R.N.
Dietary Changes to Prevent and Reduce Stone Formation
Increase Fluid Intake
Increasing urine volume can reduce supersaturation, and is widely known to help prevent stone formation. Recommendations for urinary output vary, but there is general agreement that it should exceed two liters per day, while some even encourage urinary outputs in excess of three liters per day (Menon & Resnick, 2002; Sakhaee, Zerwekh, & Pak, 1980). A key point is that the dilution of urine is necessary "24/7," or all day, every day. A patient who voids the recommended two liters a day between the hours of 8 am and 10 pm, but only 300 milliliters during the remaining 10 hours of the day will have saturated urine overnight, with the possibility of precipitation and aggregation during the sleeping hours. Patients must accept the necessity of getting up at least twice at night to urinate, and should consume more water each time they rise to void.
Stress to patients that it is not the quantity of fluid consumed that is important, but rather the fluid voided that should be measured. Patients living in hot or dry conditions, or who exercise and perspire significantly, will need to drink even more liquid to maintain adequate urine output.
Many patients ask what fluids are recommended, and which are prohibited. The simple answer is that water is best. For those with excessive urinary oxalates, black tea should be eliminated because black tea is a high-oxalate beverage. Curhan, Willett, Rimm, Speizer, and Stampfer (1998) found, in a retrospective study of previously non-stone forming women from the Nurses' Health Study, that the type of beverages consumed proved relevant for stone formers. Of the 17 beverages studied, and after correcting for other contributing factors, those who drank one daily 8 ounce glass of grapefruit juice had a 44% increased risk of a stone event in the 8-year period, while the risk was decreased by 8% to 10% for each daily 8 ounce serving of coffee (both caffeinated and non-caffeinated), tea, or wine. A prospective study had similar conclusions for men, additionally showing that beer had a protective effect and apple juice increased the risk of stone events (Curhan, Willett, Rimm, Speigelman, & Stampfer, 1996). Also, a study published by Massey and Sutton (2004) showed a modest positive relationship between caffeine intake and urinary calcium levels in stone formers and non-stone formers, so caffeinated beverages should be limited in stone formers. In summary, stone formers should drink more water and avoid excess caffeine, black tea, and grapefruit and apple juices.
What do these studies mean for patient education? Water is the best beverage for stone formers. It is non-caloric, non-caffeinated, and contains insignificant amounts of solutes. In initial attempts to increase patients' fluid intake, it may be appropriate to advise them to drink whatever they can consume in large quantities. However, warning them of side effects of sugared and caffeinated beverages in large quantities is important. The results discussed above indicate that consumption of alcoholic beverages is unlikely to increase stone risk. Water that tastes good (filtered, reverse osmosis, bottled) may be easier to consume than tap water, so encourage patients to seek a source of good-tasting water. There is no clear agreement on the impact of drinking water's mineral content on lithogenesis; "hard water" may not be problematic for most patients (Menon & Resnick, 2002). Again, water in large quantities should be the focus of prevention. Lemonade is often recommended, as it supplies dietary citrate, a stone inhibitor and pH buffer when excreted later in the urine.
Encourage patients to set consumption goals, carry water with them at all times, and strive for pale urine throughout the day and night. Some patients describe an initial physiologic resistance to increased fluid intake which eases as their bodies and minds learn the new habit of extra fluid intake and output. According to Parks, Goldfischer, and Coe (2003), aims by clinicians to increase patients' urinary volumes often fall short, and follow-up metabolic studies showed an average increase in urine output of only 0.3 liters per 24 hours. This increase was associated with a curious increase in sodium intake. High urine volumes should be the goal of all patients who form stones. In this instance, more is definitely better. Most patients find that after forcing fluids for a couple of months, their bodies crave fluids and their habit is to drink more.
Consume Adequate Calcium
High urine calcium, hypercalciuria, is associated both with formation of kidney stones and with osteoporosis. Sufficient calcium intake is required for the growth and maintenance of the skeleton in children and adults. Reducing urine calcium should be a goal for stone formers, but not via dietary restriction. While reduced dietary calcium can decrease urine calcium (Lemann, 2002), calcium restriction is no longer advisable for patients who form calcium kidney stones as this puts them at risk of bone disease, namely osteoporosis. Recall that bones are in a constant process of resorption and formation; adequate calcium is required for the ongoing rebuilding of bone material.
Several recent studies have shown, in fact, that adequate calcium intake is associated with decreased stone formation. Curhan, Willett, Knight, and Stampfer (2004) found that in previously non-stone forming younger women, higher intake of dietary calcium was related to lower risk of kidney stone formation. Additionally, a 5-year randomized clinical trial of men with a history of calcium oxalate stones found that a normal calcium, decreased sodium, and decreased animal protein diet was more effective for reducing stone events than was a restricted calcium diet (Borghi et al., 2002). So, adequate calcium plus decreased sodium and protein intake had a significantly more protective effect against stones than decreased calcium intake alone.
Why might increased dietary calcium reduce the risk of calcium stone formation? Calcium and oxalate bind in the gut and in the urine to form a nonabsorbable compound. Low dietary calcium permits greater free oxalate to be absorbed in the gut and excreted in the urine, which may be counterproductive for calcium oxalate stone formers. Restricted calcium intake results in increased urinary oxalates, a risk for stone formation (Menon & Resnick, 2002). This is a proposed cause of the association between reduced calcium intake and increased supersaturation of calcium oxalate (Lemann, 2002).
Clearly, strong research evidence now supports adequate calcium intake for patients who form kidney stones. Low-fat dairy products, green leafy vegetables, broccoli, fortified foods, and almonds are excellent sources. Patients should consume enough dietary calcium to meet (but not exceed) the United States Recommended Daily Allowance (RDA) of calcium, which ranges from 1,000 to 1,200 milligrams daily for adults. The recommendations are the same for men and women, but vary by age group (see Table 1 ). Patients should avoid calcium supplements in favor of calcium-rich foods; a patient with intolerance to dairy products may supplement, but should not exceed the RDA for his/her age group.
Limit Dietary Oxalates
Oxalate is found in many foods, but there is considerable variability in the amount, which depends upon where the food is grown. Likewise, individual absorption of oxalate also varies, which makes adequate calcium intake critically important. Nonetheless, oxalate restriction should be attempted. The highest levels of oxalate are found in chocolate, nuts, beans (including soybeans), rhubarb, spinach, beets, and black tea. A thorough oxalate list can be found on the Web site of the Oxalosis and Hyperoxaluria Foundation (http://www.ohf.org/diet.html). This list is exhaustive and may be overwhelming to patients. Stress that reduction of high oxalate foods is the goal for typical stone formers rather than strict avoidance of all oxalate-containing foods (which would be very difficult). Followup 24-hour urine studies will demonstrate the adequacy of patients' restriction.
Though only 10% to 20% of urinary oxalates come from dietary sources (Morton, Iliescu, & Wilson, 2002), dietary reduction is commonly advised for calcium oxalate stone formers. It has been suggested that because there is much less oxalate in the urine than calcium in the urine, urinary oxalate concentration is much more critical to the formation of calcium oxalate crystals than is the urinary calcium concentration; reducing urine oxalates may have a more powerful effect on stone formation than can reduction of urine calcium (Morton et al., 2002). Patients with calcium oxalate stones, particularly those with documented hyperoxaluria, should avoid foods high in oxalates. Vitamin C is a precursor to endogenous production of oxalates, so some clinicians recommend avoiding mega-doses of vitamin C. The rare genetic condition of primary hyperoxaluria is only slightly impacted by dietary reduction, and causes serious medical problems besides kidney stones.
Limit Sodium Intake
Because calcium and sodium compete for reabsorption in the renal tubules, excess sodium intake and consequent excretion result in loss of calcium in the urine. High-sodium diets are associated with greater calcium excretion in the urine (Lemann, 2002). Metabolic studies often reveal exceptionally high urine calcium over 24 hours, related to patients' exceptionally high sodium excretion. Patients may deny salt intake, stating, "I never salt my food!" They quite likely are ignorant of hidden sodium sources in the diet. Sodium is a common preservative in canned and frozen foods, and is endemic in restaurant foods. Instruction on careful inspection of food labels and wise food choices helps patients identify and reduce sodium in their diets.
A notable dietary "ah-ha!" was the admission by one patient that, on the day of 24-hour urine testing, she ate a full jar of pickles to reduce stress, and then drank the brine; needless to say, her urine sodium was very high on the day of her stress mitigation.
The role of the nurse or dietician in shedding light on sources of sodium cannot be underestimated. Repeated, persistent inquiry into dietary habits may be necessary. The goal of therapy should be a "no added salt diet," or the equivalent of 2,000 mg per day or less of dietary sodium. Reduction of dietary sodium is difficult and disappointing to patients. They may believe they have made significant reductions and sacrifices, while their urine sodium remains high. Consultation with a registered dietician may help the patient achieve the specific goal of a sodium intake of 2,000 milligrams or less per day.
Limit Animal Protein
The effect of excess animal protein (purine) is most obvious for the uric acid stone former. Uric acid, a byproduct of purine metabolism, is excreted in large quantities in the urine. Excess protein creates urine with high total urine uric acid, potentially high supersaturation of urine uric acid, and a low pH, necessary for formation of uric acid stones. There is no inhibitor of uric acid crystal formation (Menon & Resnick, 2002), so dietary measures focus on reducing uric acid and increasing urine volume. Reduction of animal protein to 12 ounces per day for adults is recommended. This is plenty to meet the dietary needs of most Americans, many of whom typically consume several more ounces of animal protein daily than is recommended. Protein from plant sources (beans, legumes, etc.) can be substituted as a dietary alternative without negative consequences. Calcium oxalate stone formers reducing their animal protein should note the oxalate content of substitute proteins.
The role of excess protein in promoting calcium stone formation is less obvious, but equally important. High dietary protein is associated with increased urinary calcium. Thus, there is a link between meat consumption and both uric acid and calcium stone formation. In fact, vegetarians form stones at one-third the rate of those eating a mixed diet (Lemann, 2002). A study of 18 hypercalciuric stone formers found that a 15-day protein restriction had many positive effects on urinary markers of stone risk. Namely, significant decreases were seen in urine calcium, urine uric acid, urine phosphate, and urine oxalate. And, for unclear reasons, a beneficial increase in urinary citrate was observed (Giannini et al., 1999). Citrate is a known inhibitor of calcium oxalate crystal formation and also increases pH, which can prevent uric acid stones. Clearly, the benefits of protein restriction for stone formers are many.
A relationship between weight, body mass index and risk of calcium oxalate stone formation was established in a retrospective study of health professionals. Curhan and colleagues (1998) found that "the prevalence of stone disease history and the incidence of stone disease were directly associated with weight and body mass index. However, the magnitude of the associations was consistently greater among women" (p. 1645). The value of weight loss for stone prevention has not been proven, but given the benefits of weight loss for general health, it is certainly worth mentioning to overweight patients who form stones.
There are excellent resources on the Internet for patients seeking nutritional information. One stellar example is NutritionData (www.nutritiondata.com). Here patients can search by general food category, like "pickle," to view the standard sodium content, as well as a plethora of additional information regarding vitamin and mineral content, calories, suggested healthier substitutes, and even the individual amino acid compositions of each protein. The site also provides detailed information about thousands of specific brand items from grocery and fast food restaurants. Under "Tools," patients can search within food categories like "dairy products" for choices highest in calcium and lowest in sodium. This site is complex and may be overwhelming to patients without good computer and Web skills, but is extraordinarily comprehensive; unfortunately, this site does not list oxalate content. For that purpose, refer patients to www.ohf.org.
For patients without Web access, nurses might find it helpful to review a general nutrition book for charts and diagrams to help patients understand nutrition content. Show patients a sample food label from a can of soup so they know where to find sodium content on foods at home. For a simple list of high-oxalate foods, visit New Urine Test Helps Find Bladder Cancer Recurrences
Inexpensive Test Improves Accuracy of Standard Follow-up
January 20, 2006 05:03:32 PM PST
Summary: A simple urine test may help doctors find more relapses in people who have had bladder cancer, according to a new study. The test was used along with cystoscopy, a visual exam of the bladder using a long lighted tube. Together, the two tests found 99% of recurrences, researchers reported in the Journal of the American Medical Association.
Why it's important: People who have had bladder cancer are at very high risk of getting it again. There are about 500,000 bladder cancer survivors in the US, the researchers note. Most survivors have to be checked for a relapse every 3 to 6 months for the first few years after their initial treatment, and every year after that. Cystoscopy is the main way to look for recurrences, but it can't always find all of them. As a backup, doctors usually use urine cytology, a lab analysis that looks for cancer cells in urine. But this test also misses many cancers.
Patients and doctors need better ways to find bladder cancer recurrences early so they can be treated promptly. If a relapse is caught early, the patient has a better chance of surviving, said lead study author H. Barton Grossman, MD, professor of urology at the University of Texas M.D. Anderson Cancer Center.
What's already known: The new urine test, called BladderChek, measures the protein NMP22. High levels may signal bladder cancer. On its own, the NMP22 test hasn't been very accurate at finding bladder cancers. But researchers thought it might be better than urine cytology at finding cancers that cystoscopy missed.
BladderChek has several advantages over urine cytology and other urine tests that are used to look for bladder cancer relapses. It can be done in a doctor's office and usually gives results within 30 to 50 minutes. It is also less expensive and less complicated than urine cytology, which must be performed by trained specialists in a laboratory. It is already approved by the US Food and Drug Administration for helping diagnose bladder cancer and for helping find relapses. The test's manufacturer, Matritech, Inc., was involved in designing, funding, and reviewing the current study.
How this study was done: The researchers recruited 668 bladder cancer survivors who were being followed-up at 23 facilities across the US. Before having cystoscopy, each patient gave a urine sample. Part of that sample was used for the BladderChek test, and part was used for standard urine cytology. The researchers gauged the cancer detection rate of each of the 3 methods alone, and of each urine tests combined with cystoscopy.
What was found: Bladder cancer was diagnosed in 103 patients. Cystoscopy was the most accurate test, finding 94 of those cancers (91%) all by itself. The BladderChek test alone found only 51 cancers. But BladderChek combined with cystoscopy found 99% of the cancers. In fact, the BladderChek test found 8 of the 9 cancers that cystoscopy missed.
"We depend on the urine test to show us whether there's a possibility of cancer that we're not seeing with the scope," explained Barry Stein, MD, a co-author of the study and professor of urology at Brown Medical School in Rhode Island. "If the result is positive and you didn't see anything from the cystoscopy, you would check to see if you missed something."
Urine cytology also improved the performance of cystoscopy, but not by as much. It found only 3 of the 9 cancers cystoscopy missed. Together, the 2 tests found 94% of cancers, but that improvement was statistically no better than cytoscopy alone. Urine cytology alone found just 12 cancers. That's unusually poor performance for urine cytology, said Samuel Cohen, MD, PhD. He's a professor of oncology and chair of pathology and microbiology at the University of Nebraska Medical Center and a member of the panel that wrote the bladder cancer treatment guidelines for the National Comprehensive Cancer Network. He was not involved in the new study.
The study did not look at what happened to the patients after their relapse was detected.
The bottom line: The results of this study suggest the BladderChek test could be a useful tool for improving detection of bladder cancer recurrences and reducing the cost of follow-up care, the researchers say. It also raises some intriguing questions about whether it might be possible to find these recurrences earlier, said Len Lichtenfeld, MD, deputy chief medical officer for the American Cancer Society. He was not involved in the study.
"If [this test] were able to pick up a recurrent cancer before it could be seen," he said, "would that mean that some of the more aggressive cancers could be treated more effectively, with a greater rate of long term survival? We know that the longer a recurrence of bladder cancer is present, the more difficult the situation for the patient. So, earlier detection of a recurrent bladder cancer translates into better treatment."
But this study, while promising, isn't enough to say for certain that the BladderChek test is better than urine cytology, Cohen said. It's also not enough to tell whether this new urine test really can improve outcomes for patients by finding their cancer earlier. For that, researchers need to carry out head-to-head comparisons (randomized trials) of this test and other bladder cancer detection tests that also look at long-term patient results. The study authors call for such work in their paper. In the meantime, Grossman warns that the BladderChek test should be used only together with cystoscopy, not instead of it.
Citation: "Surveillance for Recurrent Bladder Cancer Using a Point-of-Care Proteomic Assay." Published in the Jan. 18, 2006, Journal of the American Medical Association (Vol. 295, No. 3: 299-305). First author: H. Barton Grossman, MD, University of Texas M.D. Anderson Cancer Center.
Mortality Not Higher for Most with Prostate Cancer
NEW YORK (Reuters Health) - The mortality rates for most men diagnosed with prostate cancer in the United States are no higher than those in the general population, a new analysis shows. "The bottom line is that most men diagnosed with the disease today can expect to live as long as, or longer than, men their age without the disease," two editorialists comment.
The value of prostate specific antigen (PSA) screening in reducing prostate cancer mortality is still in question, Dr. Hermann Brenner and Dr. Volker Arndt of the German Center for Research on Aging in Heidelberg report in the Journal of Clinical Oncology.
Widespread use of the PSA test in the US since the late 1980s means many more men are living with a diagnosis of prostate cancer, the physicians point out.
They used "the recently introduced period analysis methodology" to evaluate 5- and 10-year survival rates for 183,484 men diagnosed with prostate cancer between 1990 and 2000 included in the Surveillance, Epidemiology and End Results Program (SEER), a large US database.
Overall, relative 5-year survival rates for prostate cancer patients were 99 percent, and 10-year survival rates were 95 percent, Drs. Brenner and Arndt found. "That is, excess mortality compared with the general population was as low as 1 percent and 5 percent within 5 and 10 years following diagnosis, respectively," they explain.
For the two thirds of men with well or moderately differentiated localized or regional prostate cancer, there was no excess mortality at all.
The researchers note that it is possible that earlier diagnosis might not in itself mean longer survival. The question of whether PSA screening does in fact reduce mortality from prostate cancer must be answered by large-scale clinical trials, which are currently underway, they add.
In an accompanying editorial, Dr. George Wilding and Patrick Remington of the Comprehensive Cancer Center at the University of Wisconsin in Madison write: "Given the many uncertainties about this disease, this information alone will be helpful for clinicians and their patients when discussing treatment options and when considering what life will be like living as a prostate cancer survivor."
SOURCE: Journal of Clinical Oncology, January 20, 2005.
Prostate drug AVODART might cut cancer risk
Last Updated: 2004-10-15 13:45:01 -0400 (Reuters Health)
NEW YORK (Reuters Health) - Men who take Avodart (dutasteride) to treat an enlarged prostate apparently have a reduced risk for developing prostate cancer, a new study indicates.
Avodart and a similar drug, Propecia (finasteride), are technically classified as 5-alpha-reductase inhibitors. They suppress the potent male hormone dihydrotestosterone and thereby inhibit growth of the prostate in men with benign prostatic hyperplasia, commonly known as BPH.
Dr. Gerald L. Andriole from Washington University School of Medicine in St. Louis, Missouri, and colleagues used data from three recently completed trials to investigate whether dutasteride treatment, in comparison to treatment with an inactive placebo, had a meaningful effect on the rate of prostate cancer detection.
The cumulative rate of prostate cancer detected during the first 24 months of dutasteride treatment was 1.1 percent, compared with 1.9 percent in patients treated with placebo, the researchers report in the medical journal Urology.
Additional cancers reported between month 24 and month 27 slightly changed the cumulative incidence rates (1.2 percent for dutasteride, 2.5 percent for placebo), resulting in a 51 percent lower risk of prostate cancer for the dutasteride group relative to the placebo group.
Referring to another study, Andriole told Reuters Health: "The results from the Prostate Cancer Prevention Trial (PCPT), which shows that finasteride reduces the incidence of prostate cancer, strongly suggest that 5-alpha-reductase inhibition will play a key role in the reduction in risk of prostate cancer development and progression."
Based on these findings, the investigators write, a trial "has been designed to establish further the efficacy of dutasteride" for the prevention of prostate cancer.
"We anticipate complete enrollment of the trial by the spring of 2005," Andriole said, "and results should be available after participating men complete 4 years of treatment and their end-of-study biopsies."
SOURCE: Urology, September 2004.
Impotence Common After Radiation, Surgery on Prostate Tue Sep 14,11:48 PM ET
By Ed Edelson HealthDay Reporter
TUESDAY, Sept. 14 (HealthDayNews) -- A large majority of men who have surgery or external beam radiation treatment for prostate cancer are impotent five years after either procedure, a new study finds.
Previous research had found that surgery was likelier to lead to impotence in the short term, but this study from the National Cancer Institute (news - web sites) (NCI) discovered that men who had radiation underwent a decline in sexual function between two and five years later.
The incidence of urinary incontinence was higher in men who had surgery, but bowel urgency and painful hemorrhoids were more common in those who had radiation therapy, said a report on the research in the Sept. 15 issue of the Journal of the National Cancer Institute.
The study results "are one element to be considered among men who want to be treated for prostate cancer," said study author Arnold L. Potosky, an epidemiologist at the NCI's division of cancer control and prevention.
But the findings provide only partial guidance, since they do not cover the long-term side effects of hormonal therapy or implanted radioactive seed treatment, which were not available when the study began, Potosky said.
Moreover, the study says nothing that could help resolve a heightening debate about whether watchful waiting, rather than any treatment, is best for men who are newly diagnosed with prostate cancer on the basis of elevated readings of prostate-specific antigen (PSA), a test now widely used to screen for the cancer, he said.
Potosky's cautious appraisal is that, "given the uncertainty about which treatment is best in terms of survival, having information about possible side effects can be useful in determining treatment."
Other studies have shown that surgery reduces deaths from prostate cancer compared to watchful waiting, but does not improve overall survival. There have been no studies that directly compare the survival benefits of radiation therapy vs. surgery.
The new report is the latest on a study that has followed more than 1,100 men with prostate cancer that had not spread beyond the gland. Earlier reports found a higher incidence of impotence -- the inability to achieve an erection -- after two years among men who had surgery (82.1 percent) than for those who had radiation therapy (50.3 percent).
But the difference had narrowed greatly after five years, with impotence reported in 79.3 percent of the surgical patients and 63.5 percent of those who had radiation. While that difference is significant, "I'm not sure it is critical in a decision about treatment," Potosky said.
Urinary incontinence was reported by 15.3 percent of men who had surgery and 4.1 percent of those treated with radiation. Bowel urgency was experienced by 29 percent of the men who had radiotherapy and 19 percent of those who had surgery, while the incidence of painful hemorrhoids was 20 percent in the radiation group, 10 percent in the surgery group."
The report is "an update on a very important study showing that interventions have a substantial impact on the quality of life" of men diagnosed with prostate cancer," said Dr. Howard L. Parnes, chief of the prostate group at the NCI's division of cancer control.
Several NCI studies now are being done to determine whether treatment is better than watchful waiting for men in screening program who have high PSA levels that traditionally have been interpreted as indicators of prostate cancer, he said. Results are not expected for several years.
The new report of a high incidence of major side effects after treatment is important because "if interventions were not toxic, you wouldn't need much proof to do an intervention," Parnes said.
"This is an issue of risk vs. benefits," he said. "The risks have been clear for a while. The benefit is less clear."
For patients and doctors, Parnes recommends "a cautious approach, which takes both risk and benefit into account."
Inventor of PSA Cancer Test Says It's Overused Fri Sep 10, 3:34 PM ET
NEW YORK (Reuters Health) - For many men, a routine PSA blood test to screen for prostate cancer has become an annual ritual. Now the developer of the test says it can't be relied on for this purpose, and has led to overly zealous treatment of men with prostate enlargement.
Dr. Thomas A. Stamey at Stanford University first reported in 1987 that levels of PSA in the blood could be used as a marker of prostate cancer.
"What we didn't know in the early years is that benign growth of the prostate is the most common cause of a PSA level between 1 and 10 ng/mL," Stamey notes in a university press release. Standard units of measurement of PSA are nanograms per milliliter (ng/mL) of blood.
Stamey's group found that the average size and invasiveness of prostate cancers have been dropping over the past two decades, to the point that the cancers being discovered may not be clinically meaningful.
The investigators examined tissue from 1317 prostates removed at Stanford since 1983. During the first 5-year period, 91 percent of cancers were obvious on digital rectal examination (DRE), and average volume of the cancer was 5.33 cc. Between 1999 and 2003, these values had declined to 17 percent and 2.44 cc.
Also, the degree to which the tumor had penetrated the wall of the prostate dropped from an average of 1.54 to 0.22 centimeters between the two periods.
What has happened, Stamey and his colleagues suggest in the Journal of Urology, is that prostate cancer is being over-treated, given that most men will develop the disease if they live long enough and the fact that death from prostate cancer is uncommon in elderly men.
The authors conclude that the extensive use of PSA screening is not warranted. Instead, they recommend "careful palpation of the prostate" by DRE -- since cancers found in this way "almost always require some form of treatment."
SOURCE: Journal of Urology, October 2004.
Garlic and prostate cancer. A member of the same family as onions, leeks and scallions, garlic appears to reduce the risk of many types of cancer, including prostate cancer. It's thought that sulfur compounds in garlic enhance immune function, which helps combat tumor growth. These compounds may also slow the spread of cancer cells and increase the production of enzymes that help eliminate cancer-causing substances.
Green tea and prostate cancer Made from tea leaves dried and fragmented soon after harvesting, green tea contains a natural substance called epigallocatechin gallate (EGCG). This compound appears to inhibit enzyme activity necessary for cancer growth, but large-scale studies haven't evaluated this theory.
Oral Consumption of Green Tea Polyphenols Inhibits Insulin-Like Growth Factor-I–
Induced Signaling in an Autochthonous Mouse Model of Prostate Cancer
Vaqar Mustafa Adhami1, Imtiaz Ahmad Siddiqui1, Nihal Ahmad1, Sanjay Gupta2 and Hasan Mukhtar1
1 Department of Dermatology, University of Wisconsin, Madison, Wisconsin; and 2 Department of Urology, Case Western Reserve University and the University Hospitals of Cleveland, Cleveland, Ohio
We earlier demonstrated that oral infusion of green tea polyphenols inhibits development and progression of prostate cancer in transgenic adenocarcinoma of the mouse prostate (TRAMP) model. Evidence indicates that elevated levels of IGF-I with concomitant lowering of IGF binding protein (IGFBP)-3 are associated with increased risk for prostate cancer development and progression. In this study, we examined the role of IGF/IGFBP-3 signaling and its downstream and other associated events during chemoprevention of prostate cancer by green tea polyphenols in TRAMP mice. Our data demonstrated an increase in the levels of IGF-I, phosphatidylinositol 3'-kinase, phosphorylated Akt (Thr-308), and extracellular signal-regulated kinase 1/2 with concomitant decrease in IGFBP-3 in dorso-lateral prostate of TRAMP mice during the course of cancer progression, i.e., as a function of age. Continuous green tea polyphenol infusion for 24 weeks to these mice resulted in substantial reduction in the levels of IGF-I and significant increase in the levels of IGFBP-3 in the dorso-lateral prostate. This modulation of IGF/IGFBP-3 was found to be associated with an inhibition of protein expression of phosphatidylinositol 3'-kinase, phosphorylated forms of Akt (Thr-308) and extracellular signal-regulated kinase 1/2. Furthermore, green tea polyphenol infusion resulted in marked inhibition of markers of angiogenesis and metastasis most notably vascular endothelial growth factor, urokinase plasminogen activator, and matrix metalloproteinases 2 and 9. Based on our data, we suggest that IGF-I/IGFBP-3 signaling pathway is a prime pathway for green tea polyphenol-mediated inhibition of prostate cancer that limits the progression of cancer through inhibition of angiogenesis and metastasis.
RED MEAT AND PROSTATE CANCER
“There’s a general consensus that saturated fat or red meat is associated with a higher risk of prostate cancer,” says June Chan of the University of California at San Francisco. But so far, studies haven’t been able to tease out what it is in meats or dairy foods that may cause prostate cells to go haywire. Saturated or animal fat is a leading possibility. Among the others:
Red meat. In 1993, Harvard researchers reported that men who ate red meat (beef, pork, lamb, or veal) most frequently had more than double the risk of advanced prostate cancer compared to men who ate those meats least often This year, they updated their findings on the study, which tracks more than 50,000 men.
“Our study still suggests that the less red meat you eat, the better,” says Harvard’s Edward Giovannucci.
Why red meat? Cooking the meat at high temperatures produces heterocyclic amines, which may promote cancer. “It could also be the animal fat or the high calorie-density of diets rich in red meat,” says Giovannucci. “We’re not sure which.”
If animal fat were a culprit, as some studies suggest, high-fat dairy foods like whole milk and cheese would also put the prostate at risk. But it’s also possible that the calcium in dairy foods poses a threat.
Calcium. It cuts the risk of osteoporosis and possibly colon cancer. And low-fat milk and other dairy foods can help prevent high blood pressure (though not necessarily because of their calcium).
So how could too much calcium promote prostate cancer? The theory: The active form of vitamin D—which we get mostly from sunlight—may protect the prostate And calcium lowers levels of active vitamin D in the blood.
Don’t panic. Not all studies see a link between calcium and prostate cancer. And most men never reach the “too-much-calcium” range.
“Calcium may really be only a concern for men who get more than 2,000 milligrams a day,” says Chan. So it’s still safe to shoot for the latest Recommended Dietary Allowances (RDAs)—1,000 mg a day for men 50 or younger and 1,200 mg for men over 50. (That includes what you get from food and supplements.)
The evidence isn’t strong enough to recommend that men change their calcium intake, she adds. “But they should be aware of the association between calcium and prostate cancer, because they may be getting calcium from fortified foods and not even know it.”
Would it help to simply boost your vitamin D intake?
“Whether vitamin D is related to prostate cancer is still an open question,” says Giovannucci. “But it’s prudent to get adequate vitamin D from a multi-vitamin or sunlight.” Fatty fish and fortified foods are also sources.
1: Journal of the National Cancer Institute 385: 1571, 1993.
2: Cancer Research 58: 442, 1998.
Millions of men who have prostate cancer want to know whether diet or supplements can slow or stop the disease. But so far, research has yielded few answers.
For example, in a Canadian study of 384 men with prostate cancer, those who consumed the most saturated fat were three times more likely to die of the disease over the next five years than those who consumed the least But it isn’t clear from this less-than-perfect study that saturated fat made the difference.
prostate cancer and seven herbs called PC-SPES
Researchers are more confident that a mixture of seven herbs called PC-SPES may slow advanced cancer in men who have no other treatments available. But the pricey supplement may be no more safe or effective than taking an ordinary estrogen pill.
“Many of the herbs that my prostate cancer patients take do nothing,” says William Oh, a researcher and oncologist at Harvard Medical School and the Dana Farber Cancer Institute in Boston. “PC-SPES has effects that are visible to all doctors who work with it, but whether it is any more effective than giving estrogen, we don’t know.”
Oh tracked 23 advanced cancer patients who had been taking six capsules (1,920 milligrams) of PC-SPES a day “Half had more than a 50 percent drop in PSA levels and many had a decrease in symptoms and relief from bone pain,” he reports. “If we can reduce PSA levels significantly, we can predict that they’ll live longer and better.”
But his study and two others like it aren’t definitive, in part because they didn’t compare PC-SPES to anything else. A new clinical trial will. Oh and colleagues will study men whose cancer is progressing even though they’re taking drugs that block testosterone. Half will get PC-SPES; the others will get an estrogen called DES, or diethylstilbestrol.
“We know PC-SPES has hormonal effects like estrogen,” says Oh. “We’re trying to understand to what extent PC-SPES’s effect is due to its estrogen activity.”
That’s why taking PC-SPES is not a good strategy for men who want to prevent prostate cancer. Like estrogen, PC-SPES can cut testosterone to castration levels. “It’s like getting your testicles removed,” explains Oh. “Eunuchs don’t get prostate cancer, but it’s not a price most men are willing to pay.”
What’s more, PC-SPES isn’t as safe as its over-the-counter availability implies. “It has all the side effects of taking estrogen, like nipple tenderness, breast swelling, hot flashes, and fatigue,” cautions Oh. “And the most dangerous side effect is blood clots, which occur in an estimated five to ten percent of patients.
“Clots can stay in the legs or they can break off and go to the lung, which is more serious,” he explains. “In men who have underlying heart disease, the clot can get lodged in a coronary artery,” causing a heart attack.
Those risks may be worth taking for men who have failed the usual anti-testosterone treatment. In fact, Oh now recommends it to all men in that condition. “Their life expectancy is about 12 months,” he says. But a risky supplement that can cost more than $300 a month is not a good gamble for anyone else.
Says Oh: “Right now we have no evidence that PC-SPES prolongs life, but it can reduce the symptoms of cancer and control the disease for some period of time in men who have limited options.”
1: European Urology 35: 388, 1999.
2: Urology 57: 122, 2001.
SEVEN WAYS THAT MAY HELP PREVENT PROSTATE CANCER
1. While it's too early to say for sure, these steps may reduce the risk of prostate cancer:
2. Limit red meat, full-fat cheese, and other fatty animal foods.
3. Eat seafood-especially fatty fish like salmon-three or four times a week.
4. Eat healthy tomato-rich dishes (spaghetti or other pastas, not lasagna or pizza) at least twice a week.
5. Consider taking a daily supplement with 200 micrograms (mcg) of selenomethionine or high-selenium yeast. (If you're looking for SelenoExcell high-selenium yeast, check the ingredient list. It's found in some selenium and multivitamin-and-mineral supplements.)
6. Get some gamma-tocopherol in your diet. Soy oil (often used in salad dressings), corn oil, and sesame oil are good sources. (Some vitamin E supplements contain both alpha- and gamma-tocopherol, but many labels don't say how much gamma you're getting.)
7, Limit calcium intake from food and pills to 1,200 mg a day and take a standard multivitamin with 400 IU of vitamin D.
SELENIUM AND PROSTRATE CANCER
In the 1980s, when Larry Clark and colleagues assigned 1,300 people to take either 200 micrograms of selenium or a placebo every day, no one suspected that selenium might prevent prostate cancer. Their goal was to see whether it could prevent skin cancer in residents of the Southeast, where the soil—and people’s diets—are selenium-poor
“Selenium supplements had no effect on the recurrence of skin cancer,” Clark told Nutrition Action Healthletter in 1996. “But the three leading cancers—lung, prostate, and colon—all decreased.”
Decreased by an unheard-of two-thirds, that is. The researchers had to stop the study three years early because the selenium-takers fared so much better that it would have been unethical to keep people on the placebo.
Still, Clark was cautious about his findings. “Selenium is not going to help everybody, and it’s not going to cure all cancer,” he explained.
It’s possible that selenium only works in people who get too little from their food...or that Clark’s results were a fluke.
But worth another trial? You bet.
The National Cancer Institute (NCI) doesn’t expect results from its new trial, called SELECT, for about a decade (see “SELECT One Option,”). Meanwhile, some researchers are worried that SELECT may not be using the right kind of selenium supplement.
Clark’s trial used a high-selenium yeast. (SelenoExcell is the brand that is closest to the supplement Clark used—see “The Bottom Line,”.) SELECT will use selenomethionine, which is the most abundant form of selenium found in the yeast. An expert panel recommended selenomethionine instead of yeast because selenium and other constituents of the yeast vary too much from batch to batch, explains the NCI’s Demetrius Albanes.
Let’s hope it was the right choice.
“I’m concerned that there might be some bioactive compounds in the yeast that aren’t in the selenomethionine supplements,” says Byers, who served on a safety committee for the 1996 study. “If the new study fails, we won’t know why.”
tomato sauce two to four times a week had a 34 percent lower risk of prostate cancer
Spaghetti sauce and pizza were big news in 1995. That’s when Giovannucci’s team found that men who consumed tomato sauce two to four times a week had a 34 percent lower risk of prostate cancer than men who ate no tomato sauce
The possible protector: lycopene, a carotenoid found in tomatoes that’s easier to absorb if they’re cooked
“Lycopene scavenges free radicals and suppresses damage due to oxidation in the tissues,” explains Northwestern University’s Peter Gann. “As an antioxidant, it’s more potent than beta-carotene. And it’s concentrated in the prostate.”
In 1999, Gann, Giovannucci, and their colleagues found a lower risk of prostate cancer in men who had higher blood lycopene levels 13 years earlier
“Not every study shows a benefit, but the ones that were best able to detect an association found it,” says Giovannucci.
Also encouraging: Researchers often wonder if people who take vitamins or eat more fish are more health-conscious, which could confound their results. But there’s less reason to think that pizza and spaghetti eaters are more health-conscious.
Still, Giovannucci’s research is no excuse to load up on lasagna, pizza, or other saturated-fat-laden foods.
“It’s not proven, but eating spaghetti sauce twice a week could certainly be part of a healthy diet,” says Giovannucci. “Eating ten pizzas a week isn’t.”
soy might lower the risk of prostate cancer,
“There’s a strong biological basis for thinking that soy might lower the risk of prostate cancer,” says Mark Messina, a soy expert who is an adjunct professor at Loma Linda University in California and a consultant to the soy industry.
Among the promising clues: In Asia, where tofu and other soy foods are a regular part of the diet, prostate cancer rates are low. And the isoflavones in soy foods inhibit the growth of prostate cancer cells in animals and test tubes.
But when it comes to people, the evidence is thin. “You could put all those animal and test-tube studies in a basket and one good human clinical study would outweigh them,” says Messina.
Large U.S. studies can’t even look at soy because most men don’t eat enough of it. That leaves one study in Hawaiians (it found only a weak link) and another in Seventh-day Adventists,9 That study found a lower risk only in men who drank more than one glass of soy milk a day. However, only two percent of the men drank soy milk that often, so the results aren’t rock-solid.
Also disappointing: When researchers gave men with elevated PSA levels two daily soy beverages (each with roughly 35 milligrams of isoflavones), their PSAs didn’t drop
“Our study only lasted six weeks,” notes investigator Stephen Barnes of the University of Alabama at Birmingham. “So it’s difficult to know what might have happened over the long term.”
Messina remains optimistic. “There’s a consistent story forming,” he says. “But it’s a story waiting to be confirmed.”
It’s too early to know whether selenium, vitamin E, lycopene, soy, or seafood can prevent prostate cancer. Nor is there any guarantee that cutting back on red meat or high-fat dairy foods will lower the risk. But men who follow advice for an overall healthy diet can’t lose.
“We’re not up to the point of giving recommendations on diet and prostate cancer,” says the University of California’s June Chan. “But it’s prudent to eat less meat and animal fat and more vegetables, fruits, and whole grains. There’s good reason to believe that a prudent diet is beneficial for heart disease, and it may help for cancer.”
watermelon help men avoid prostate cancer.
Juicy, red watermelon is not only delicious, it may help men avoid prostate cancer. As long as you spit out the seeds, watermelon is the biggest supplier among fresh fruits and vegetables in the antioxidant lycopene, which is believed to play a big role in the prevention of the killer disease. Antioxidants such as lycopene work in your body by disarming free oxygen radicals, which are thought to contribute to the development of many cancers. A 2-cup serving of watermelon contains 15 - 20 milligrams of this vital plant pigment. Other sources include tomatoes, red grapefruits and guavas.
Aspirin May Help Prevent Prostate Cancer
Thu Feb 12, 5:28 PM ET Add Health - Reuters to My Yahoo!
By Will Boggs, MD
NEW YORK (Reuters Health) - Taking an aspirin each day might be good for your heart, but new research suggests that it may also reduce the risk of prostate cancer.
Prostate cancer (news - web sites) is the most commonly diagnosed non-skin cancer in the U.S. and Canada, "and is second only to lung cancer in terms of number of deaths it causes," Dr. Salaheddin Mahmud from McGill University, Montreal, told Reuters Health. "So it is very unfortunate that at the moment we do not know of any modifiable risk factors for the development of this disease."
Previous reports investigating the anti-cancer effects of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) have yielded conflicting results. For this reason, Mahmud's team analyzed combined data from 12 reports to clarify the effect of these drugs on the risk of prostate cancer. The results are reported in the British Journal of Cancer.
The use of aspirin was associated with a 30 percent reduction in the risk of advanced prostate cancer and a 10 percent reduction in total prostate cancer risk, the authors note.
"NSAIDs (and aspirin in particular) appear to offer some protective effect against prostate cancer both in laboratory studies and in observational studies in humans," Mahmud said.
The study cited by the investigators as "best equipped to address this issue" reported a strong anti-cancer effect for aspirin use, but only among participants that had taken aspirin for at least 4 years.
"It is too early to recommend regular use of aspirin for prostate cancer prevention, but the time is right" for forward-looking studies specifically designed to address this topic, he added.
Recently, two large randomized controlled trials were begun to evaluate the protective effects of two of the newer NSAIDs -- Celebrex and Vioxx -- Mahmud added. "I am not aware of any...trials on the cheaper and more widely available" older NSAIDs, including aspirin.
The focus on the newer NSAIDs is partially because they have fewer side effects, such as stomach bleeding, and partially because they are more economically rewarding to drug companies, he said.
SOURCE: British Journal of Cancer, January 12, 2004.
Red Meat Gene Linked with Prostate Cancer in Study
Wed Apr 17, 6:10 PM ET
By Christopher Doering
WASHINGTON (Reuters) - A gene involved in digesting red meat is also highly active in cells taken from prostate cancer (news - web sites) tumors--a finding that could lead to new dietary and chemical treatments to prevent the disease, researchers said on Wednesday.
Cells removed from prostate tumors showed a nine-fold increase in activity by a gene called AMACR as compared to healthy cells, a team of researchers at Johns Hopkins University in Baltimore found.
The AMACR fatty acid molecule is found in high levels in dairy and beef products. The gene of the same name produces an enzyme that helps break down the fatty acid.
Previous studies have shown that diets high in red meat are linked with an increased risk of prostate cancer.
Drugs that may cause impotence
URL of this page: http://www.nlm.nih.gov/medlineplus/ency/article/004024.htm
Impotence caused by medications; Drug-induced erectile dysfunction
Various medications and recreational drugs can have an affect on sexual arousal and sexual performance. It should be noted that what causes impotency in one man may cause an erection in another.
If you suspect that a medication you are taking is having a negative effect on sexual performance, discuss the matter with your health care provider. NEVER stop taking any medication without first consulting your health care provider because some medications can produce life-threatening reactions if they are not tapered or switched appropriately.
The following is a list of medications and non-prescription drugs that may cause impotence:
Antidepressant and other psychiatric medications:
Antihypertensive and diuretic medications:
Among the anti-hypertensive medications, thiazides are the most common cause of ED, followed by beta-blockers. Alpha-blockers are, in general, less likely to cause this problem.
Anti Parkinson's disease medications:
Antiandrogens (Casodex, Flutamide, Nilutamide)
LHRH agonists (Lupron, Zoladex)
Aminocaproic acid (Amicar)
Finesteride (Propecia, Proscar)
H2 Blockers (Tegamet, Zantac, Pepcid)
NSAIDs (Ibuprofen, etc.)
Opiate analgesics (painkillers)
Oxycodone (Oxycontin, Percodan)
Working Out to Fight Impotence
Fri Jul 11, 7:01 PM ET Add Health - HealthDay to My Yahoo!
FRIDAY, July 11 (HealthDayNews) -- Pelvic floor muscle exercises can help restore erectile function in men, says a British study.
The study by researchers at the University of the West of England in Bristol found men with erectile dysfunction who did pelvic floor exercises had the same overall improvement as men in a large trial of Viagra.
The pelvic floor is made up of layers of muscle and other tissues.
This study included 55 men, average age 59, who had experienced erectile dysfunction for six months or longer. The men were given five weekly sessions of pelvic floor exercises and did daily home exercises. They were assessed at three and six months.
The study found that 40 percent of the men regained normal erectile function, 35 percent had improved function and 25 percent failed to show improvement. The pelvic floor exercises also resulted in dramatic improvement in the 65.5 percent of the men with erectile dysfunction who suffered dribbles of urine after urinating.
The findings will be published in a textbook for health professionals.
For many decades, women have been advised to perform pelvic floor exercises before and after childbirth, hysterectomy and menopause. This study indicates that it's also important for men to maintain pelvic floor muscle tone and function
Vitamin E protects against -- prostate and bladder CANCER
By Maggie Fox, Health and Science Correspondent
WASHINGTON (Reuters) - Vitamin E protects against at least two common forms of cancer -- prostate and bladder -- but popping supplements is probably not the best way to get the vital nutrient, researchers said on Sunday.
Two studies found that people who either ate the most vitamin E containing food or who had the highest levels in the blood were the least likely to have cancer.
But the researchers also noted that there are several different forms of vitamin E and the kind you eat -- in this case alpha tocopherol -- is key. And the best-absorbed form of alpha tocopherol is not found in supplements but in foods such as sunflower seeds, spinach, almonds and sweet peppers.
In one of the studies presented to the annual meeting of the American Association of Cancer Research in Orlando, Stephanie Weinstein of the U.S. National Cancer Institute and colleagues found men with the most vitamin E in their systems had the lowest risk of prostate cancer.
They looked at data from 29,133 Finnish men aged between 50 and 69 taking part in a smoker's study. All gave blood at the beginning of the study and then took vitamins to see whether the supplements might prevent various forms of cancer.
This study is best known for showing that smokers who took beta carotene, which the body converts to vitamin A, actually had higher rates of lung cancer.
Weinstein looked at vitamin E and prostate cancer, and they looked at how much E the men had in their blood before they ever took a supplement. They looked at 100 men with prostate cancer and 200 men who did not.
"We found that the men who had higher serum (blood) levels of vitamin E had a lower chance of getting prostate cancer," Weinstein told a news conference monitored by telephone.
NOT ALL E'S ARE EQUAL
Then they looked at the two main forms of vitamin E -- alpha tocopherol and gamma tocopherol.
Men with the highest natural levels of alpha tocopherol were 53 percent less likely to later develop prostate cancer. Men with the highest levels of gamma tocopherol, which only represents about 20 percent of the vitamin E in blood -- had a 39 percent lower chance.
Taking supplements further reduced prostate cancer rates.
"Nuts and seeds, whole grain products, vegetable oils, salad dressings, margarine, beans, peas and other vegetables are good dietary sources of vitamin E," Weinstein said.
In a similar study, Dr. Xifeng Wu of the University of Texas M.D. Anderson Cancer Center, John Radcliffe of Texas Woman's University in Houston and colleagues studied 468 bladder cancer patients and 534 cancer-free volunteers.
They asked their 1,000 volunteers what they ate, and estimated how much alpha-tocopherol and how much gamma tocopherol they got in their everyday diets and from supplements if they took them.
Those with the highest intake of alpha tocopherol from food had a 42 percent reduced risk of bladder cancer, and those who had a vitamin E-rich diet and took supplements too had a 44 percent lower risk.
But when broken down into types, they found gamma tocopherol offered no protection against bladder cancer.
"It would not be reckless to encourage people to try and meet the dietary allowance of vitamin E, which is about 50 milligrams a day," Radcliffe told the news conference. Current average U.S. intake of E is only 8 mg a day.
One of the best sources, said Radcliffe, a dietician, is a handful of sunflower seeds. Almonds, spinach, mustard greens and green and red peppers are also good sources of alpha tocopherol.
Many E supplements, he said, contain both active and inactive forms of E and may not be the best source. Plus, he said, sunflower seeds are high in selenium, another key nutrient, while greens are loaded with desirable nutrients.
A daily glass of pomegranate juice showed potential for slowing the growth of prostate cancer in a small study but more evidence is needed before doctors recommend it, U.S. scientists said on Saturday.
A study funded by a juice maker found men who drank the beverage had a longer time until doubling of their blood levels of PSA -- a protein that indicates the presence of prostate cancer. Patients with short doubling times are more likely to die from the cancer.
In the study, the time until PSA doubling after treatment extended to 54 months on average when the men started drinking eight ounces of pomegranate juice a day. Before drinking the juice, PSA doubled in an average of 15 months.
"That's a very big difference. ... It's an indicator of how quickly the cancer is growing," said Dr. Allan Pantuck, a urologist at UCLA Jonsson Cancer Center and the study's lead author.
Each of the 50 men who took part had radiation, surgery or other treatment for prostate cancer before enrolling in the study. No major side effects were reported from drinking the juice.
"It's too early to tell people with prostate cancer they should drink pomegranate juice" because the evidence is preliminary, Pantuck said in an interview.
A larger study is under way to try to confirm the findings, with results expected in two years, he said.
While he does not expect pomegranate juice to cure prostate cancer, Pantuck said it could delay or prevent the need for other therapies with harsh side effects including hot flashes, fatigue, depression and impotence.
Pomegranate juice "is a very non-toxic treatment that, if it really did have that effect on doubling time, could prevent many people from going on to metastatic disease and hopefully from dying of prostate cancer," he said.
The research team said substances known as polyphenols or other ingredients in the fruit juice may be able to fight prostate cancer, but exactly how is unclear. The benefits probably come from a combination of ingredients, they said.
The findings were published in the peer-reviewed journal Clinical Cancer Research and funded by a trust established by the owners of Pom Wonderful, a brand of pomegranate juice. Pom Wonderful supplied the juice used in the study.
Fish and prostate cancer
Fish that are high in fatty acids, such as mackerel, salmon or herring, may help prevent prostate cancer, according to a large study of Swedish men in the June edition of the British medical journal The Lancet.
"The main message is to eat more fatty fish," says co-author Alicja Wolk, DMSC. "Eating fatty fish reduces risk of prostate cancer by about 70%, compared to not eating it, and reduces the risk for death from the disease by about 50%." Wolk is a professor of nutrition and epidemiology at the Karolinska Institute in Stockholm, Sweden.
The study was an epidemiologic investigation, which looks at the occurrence of disease in a large population of people. The researchers followed 6,272 Swedish male twins for 30 years, examining lifestyle factors -- including diet -- and drawing associations with the risk for prostate cancer.
They found that men who consumed moderate to high amounts of fatty fish were two-to-three times less likely to develop prostate cancer than men who did not, according to the report.
Because all the men in the study were twin pairs, the researchers were able to adjust their findings to account for genetic factors. And the findings remained consistent despite other potential risk factors for prostate cancer, such as smoking and alcohol use.
The bottom line: fatty fish consumption is a powerful determinant of disease, Wolk says.
Wolk says the study contributes to accumulating evidence that the fatty acids present in fish protect against prostate cancer. Previous studies measuring the amount of fatty acids in blood have indicated that men with higher concentrations were less likely to get prostate cancer, she says.
She notes that in addition to the fatty acids, fish are a rich source of vitamins and selenium, a mineral believed to have "antioxidant" effects, preventing the oxidation of cells in the progression of cancer. "So the beneficial effects of fish may be due to a combination of all of these factors," Wolk tells WebMD.
And Wolk adds that there is accumulating evidence that the fatty oils in fish may also be good for preventing heart disease and stroke.
Urologist William Catalona, MD, who reviewed the report for WebMD, says the study offers "credible evidence" of the role of fatty fish in preventing prostate cancer.
"There is a lot of evidence that dietary factors can influence the development and progression of prostate cancer," he says. "The current view is that there are probably a handful of genes that can predispose a person to prostate cancer. But if you have an inherited susceptibility, it doesn't mean you will get it unless there is a permissive environment. A lot of the environment can be influenced by diet." Catalona is professor of urology at Washington University School of Medicine in St. Louis.
He notes that the purpose of epidemiologic studies is to raise hypotheses. More conclusive proof would be extraordinarily difficult to come by, requiring a long-term experiment directly comparing occurrence of disease in men who consumed fish and those who did not.
"As epidemiologic studies go, this provides fairly convincing evidence that, for whatever reason, men who consume larger amounts of fish are less likely to get prostate cancer," Catalona says.
And the study adds to a list of other foods that may diminish risk for prostate cancer, including green tea, tomatoes and other lycopene-containing fruits, as well as vitamin supplements, and selenium.
Lycopene is part of a family of pigments, called carotenoids, which occur naturally in fruits and vegetables.
"Patients who have prostate cancer or a family history are always asking doctors what they can do to reduce their risk," Catalona says. "Eating salmon and other fatty fish can be added to the list of foods where there is some evidence to support a beneficial effect."